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I can believe it, since people buy more of other brands which have inferior awd systems, but it just doesn't make sense. Then again, most people don't drive through deep snow, and if your town does a decent job plowing even 90:10 with variability works.

Yeah. I had a '95 Legacy with the 90/10. It was great. Loved it.

Quote:

Originally Posted by gathermewool

One thing I don't fully understand is why we can't have a number? I understand that for all practical purposes, an "active" system may redirect torque where it's needed so quickly as to be imperceptible to the operator. That doesn't mean we that there shouldn't be some base torque distribution number associated with the center diff, right? What I mean to say, is that a 90/10 AWD system has a base 10% of the torque going through the center diff to the rear wheels, and a clutch-type system engages to transfer more, right? So, that base number, before the ECM provides any input, should be easy to provide, right?

Say you are sitting at a light. It turns green and you take off. Depending on how much throttle you give it, depends on how much weight is shifted to the rear of the vehicle that the car senses and sends more power rear. That will be different pretty much every time you do it, hence not giving a set ratio.

Say you are sitting at a light. It turns green and you take off. Depending on how much throttle you give it, depends on how much weight is shifted to the rear of the vehicle that the car senses and sends more power rear. That will be different pretty much every time you do it, hence not giving a set ratio.

So, if none of the wheels experience any slip, torque will be transferred, or are you assuming the front wheels begin to slip in the above scenario?

I don't have an in-depth knowledge of all things AWD, so I can really only use my STI as an example. With the LSD center diff, the torque split at all times is a certain percentage, which is inherent to the mechanical design of the differential. To transfer more torque, the DCCD will automatically (in auto) transfer torque based on ECM inputs (or manually in manual mode.)

With that being said, what allows for the initial 10% (or whatever the number is) for a 90/10 system? Is in inherent to the design of the center diff or is it simply a byproduct of a driveshaft being connected to the center differential, and represents some minimum value, acting similarly to an open differential? Regardless, THAT is the number that should be able to be provided no matter how much it varies. This number should be static, am I right?

I can believe it, since people buy more of other brands which have inferior awd systems, but it just doesn't make sense. Then again, most people don't drive through deep snow, and if your town does a decent job plowing even 90:10 with variability works.

The active AWD systems work excellently on unplowed roads with a foot or more of snow. It's not as if it stays at 90:10. It will send much more power to the rear. 90:10 is just the default value.

With that being said, what allows for the initial 10% (or whatever the number is) for a 90/10 system? Is in inherent to the design of the center diff or is it simply a byproduct of a driveshaft being connected to the center differential, and represents some minimum value, acting similarly to an open differential? Regardless, THAT is the number that should be able to be provided no matter how much it varies. This number should be static, am I right?

The gearing of the differential sends 90% of the torque to the front when there is no slip (open diff condition). When slip is detected, the diff locks, sending some of the torque from the front to the rear (close to 50/50 at full lock). If you can imagine the front wheels being on ice, and the rear wheels being on pavement, at open diff condition the rear wheels would only be able to provide 10% of the engine torque. If there was a slight grade the car wouldn't be able to move with this low torque. With the active center diff, the car detects the front wheels slipping and applies some of the torque from the front wheels to the rear, up to 50% of the available torque. This means in the same situation where the front wheels are on ice and the rear is on pavement, the rear wheels would have a lot more torque available once the diff locks up. The difference between different types of AWD systems is how effectively they are able to move the torque around to different wheels.

Giving a set ratio on a system like the active AWD seems a bit misleading since it's not rear wheel biased like the VTD AWD or set to a ratio for performance like the DCCD on the STI. And it varies the power where it is needed based on the information the sensors are picking up. There are pros and cons to having a set bias and there are pros and cons to having a physical limitation of how much power the system can transfer to the rear, front, or side wheels.

I guess giving a set ratio of what it CAN do, at least for the active AWD system, seems plausible. It seems like people want to know the ratio so they can brag about it or judge the system based on how much it can transfer? It's not like it's going to stay at that number you so dearly want to know when you're driving anyways.

The gearing of the differential sends 90% of the torque to the front when there is no slip (open diff condition). When slip is detected, the diff locks, sending some of the torque from the front to the rear (close to 50/50 at full lock). If you can imagine the front wheels being on ice, and the rear wheels being on pavement, at open diff condition the rear wheels would only be able to provide 10% of the engine torque. If there was a slight grade the car wouldn't be able to move with this low torque. With the active center diff, the car detects the front wheels slipping and applies some of the torque from the front wheels to the rear, up to 50% of the available torque. This means in the same situation where the front wheels are on ice and the rear is on pavement, the rear wheels would have a lot more torque available once the diff locks up. The difference between different types of AWD systems is how effectively they are able to move the torque around to different wheels.

That's what I thought, thanks for the help!

Quote:

Originally Posted by A W

Giving a set ratio on a system like the active AWD seems a bit misleading since it's not rear wheel biased like the VTD AWD or set to a ratio for performance like the DCCD on the STI. And it varies the power where it is needed based on the information the sensors are picking up. There are pros and cons to having a set bias and there are pros and cons to having a physical limitation of how much power the system can transfer to the rear, front, or side wheels.

I guess giving a set ratio of what it CAN do, at least for the active AWD system, seems plausible. It seems like people want to know the ratio so they can brag about it or judge the system based on how much it can transfer? It's not like it's going to stay at that number you so dearly want to know when you're driving anyways.

Sometimes it's just curiosity Comparing AS tires to AS tires, my old '97 LGT got me through the snow better than my STI does (narrower tires with more sidewall, and less power made up for the "inferior" AWD system, I guess )

The gearing of the differential sends 90% of the torque to the front when there is no slip (open diff condition). When slip is detected, the diff locks, sending some of the torque from the front to the rear (close to 50/50 at full lock). If you can imagine the front wheels being on ice, and the rear wheels being on pavement, at open diff condition the rear wheels would only be able to provide 10% of the engine torque. If there was a slight grade the car wouldn't be able to move with this low torque. With the active center diff, the car detects the front wheels slipping and applies some of the torque from the front wheels to the rear, up to 50% of the available torque. This means in the same situation where the front wheels are on ice and the rear is on pavement, the rear wheels would have a lot more torque available once the diff locks up. The difference between different types of AWD systems is how effectively they are able to move the torque around to different wheels.

There is no gearing because there is no center differential in Active AWD. It's a clutchpack that can be loaded up with enough hydraulic pressure to either send 10% of the torque to the rear axle or 40% to the rear axle. Since the amount of friction in the clutchpack is largely irrelevant on dry pavement (since there is no torque biasing to speak of), it's really a moot point until you start to get slippage on one or both axles.. At which point the real world torque being sent to the rear wheels could be anywhere from 100-0% depending on where the traction exists.

These figures are mostly academic and in no way comparable to the 35:65 split ofva DCCD or VTD system, nor can it be compared to the "50:50" of a non-STI MT Subaru, which has a traditional geared differential.

Look, to answer the guy's question: they'll both be just fine on snow covered roads with the appropriate tires and some sensible driving. Your cross-shopping of these two vehicles is bad, and you should feel bad. Shop for something that fits your needs and desires... don't just buy **** because it's new this season... that's how an idiot buys a car.

They could at least have a factory order program, and build the vehicle to order, like they did with some Legacy GTs.

Or they could do a Spec.B or tuned by STI package, 3-500 units, special edition, painted a couple of bold colors. With a manual transaxle, that would be more of an enthusiast draw than pumpkin orange paint.

An FB25 engine, or better yet, an FA20DIT engine paired to that manual transaxle, basically making equivalent to what the next WRX is likely to be.

Maybe after WRX debuts, XV will get a commensurate model... I guess we'll find out. But I am not holding much faith left for Subaru, after so many disappointing new AWD products.

We have received many complaints about your team player attitude, specifically the lack thereof. Reluctantly, we have decided to include this in your permanent record.

Included in this record will be your recent outcry of lack of faith in Subaru.

We would like you to know that Subaru has seen exponential growth 4-5 years running. Subaru has set sales records again, both for the month of October and have already surpassed '11 sales, with 2 months left in the year.

History, dear sir, has proven you wrong, once again. It may behoove you to adjust that attitude problem of yours.

While we (the forum members) cannot make you leave (mods can, but for some reason don't), we would like to remind you the door to leave this place is ... right over there. Feel free to make your way through it, never to return.

Back off topic, SOA has continued their lack of an opinion on Active AWD...

Quote:

Originally Posted by SOA Customer Service

Dear [Snow Drift]:

Thank you for taking the time to contact us and for your continued interest in Subaru products.

I have been with Subaru of America, Inc. for 17 years now. We have not stated a torque split for our Active All-Wheel Drive (AWD) System. That may be the most asked question about our AWD Systems. But, we have never stated a torque split front-to-rear like we do for the other AWD Systems. This Active AWD System is always fluctuating with torque split, which is why we do not state a "normal" torques split.

I regret, [Snow Drift], that I could not provide you with the response you were hoping to receive.

Quick question with those with the CVTs, what RPM is it at when doing 70-75?

The 5MT that I tested yesterday was doing about 3k at 70... Is it lower at highway speeds in the CVT? How much?

Also, I noticed a bit of road noise from the tires and a bit more wind noise than I'm used to.

--kC

I believe it is around 2500 at those speeds on the highway. I have been keeping my speeds down since mine has only 500 miles on it so far. if I remember I'll take the highway home today and crank it up a little.

I think the tires are noisy too. When they are worn out I just won't buy the same thing. That is how I am looking at it.

I do feel that it is overall a little bit louder to drive but I always notice a difference when I go from a legacy platform (my old baja) to an impreza platform.

OK. Then that's where the gas savings are. I just need to do a caculation if the $1k for the CVT will make up for it. I guess I need to take a 5MT and a CVT on a back to back highway drive for NVH testing. As I said, the 5MT was sitting at 3k RPM for 70mph. Taking 500-700 rpm off that could conceivably keep things a bit quieter at highway speeds.

Saw a white one the other day and it looked sharp. As far as tire/road noise is concerned as in the Impreza sound proofing is on the lite side, but then again it's a 20 xxx vechile. I have found the Outbacks are very quiet for not that much more money.